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2.3.2.3
LOD Detection Process
Figure 2-17
shows the flow of the LED-open detection process.
(1) N is the number of cascaded TLC694x devices
2.3.2.4
Caterpillar Removal
The caterpillar issue is a common phenomenon caused by broken LEDs (LED open) in multiplexing LED
display applications. The cause of this LED-open caterpillar issue is that the electric charge on the
parasitic capacitance of an unselected line turns on the associated LED when OUTn is pulled down to
GND, due to the open LED on the selected line. This condition turns on the LEDs of all the unselected
lines unexpectedly while the line with the open LED is selected.
open caterpillar phenomenon.
SLVUBF4A – February 2018 – Revised June 2019
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Apply LED power supply
to next line
Figure 2-17. LED-Open Detection Process
Copyright © 2018–2019, Texas Instruments Incorporated
Write GS = FFFFh for all channels
into one of the memory BANKs
Input VSYNC command
Apply LED power supply
to Line 0
Input GCLK for one whole segment
Input READLOD command
(1)
Input 16 × N
SCLK
No
All lines finished?
Yes
End
Figure 2-18
Function-Control Description
shows the mechanism of LED
Function Control
23
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